BOOKS!!!
Tons of stores have books. Target ones are a bit more expensive,
Walmart has great prices. One of my favorite place to buy books is TJ Maxx. I have bought lots of Dr. Suess books at TJ Maxx. Board books would be great for all the ages you mentioned. Even for the baby.....Goodnight Moon; Brown Bear, Brown Bear, What Do You See?; Hungry Catepillar, etc.
For the older boys Hop on Pop, Are You My Mother, etc.
On the Today show this morning they showed Kohls is having a deal on If You Take a Mouse to the Movies.....for $5.00 you get a stuffed animal Mouse with it. There is one with a Pig too.
Some books you can write a small note to the child and saying who its from. I have some of my childhood books that my aunt gave me.